In oil and gas wells various types of well tools are placed in the production well bore of the well tubing to perform various functions. For example, such well tools may be safety valves, blanking plugs, monitoring instruments, such as temperature and pressure instruments. These well tools are placed in and retrieved by a conventional wireline or conductor line cable. It is desirable in many cases to have the ability to place multiple well tools at various depths to accomplish an overall objective. Well tools are conventionally set in landing nipples which have a positive stop shoulder, commonly known as a "no-go", and may also have a locking notch for locking the well tools therein. This leads to a complicated installation since in using multiple landing nipples the various "no-gos" must be differently sized to accommodate various operations. In setting well tools in such no-gos, the well tools generally have to be jarred to set and jarred to release which may be undesirable for various reasons.
In addition, various mechanical selective systems have been proposed in which wireline tools survey multiple profiles machined in the landing nipples for selectively landing a well tool in a desired nipple.